This invention generally relates to vehicle suspensions. More particularly, this invention relates to an arrangement for maintaining a desired dock height of a vehicle under selected conditions.
Vehicle suspensions are well known. Many arrangements for trucks or other heavy vehicles include air-based suspension components commonly known as air springs. Typical arrangements include a dump valve to exhaust air from the air springs when vehicle parking brakes are applied. As air is evacuated from the air springs, the height of the trailer or rear end of the truck (depending on the vehicle configuration) typically drops from a ride height until an appropriate suspension component rests on a jounce bumper internal to the air springs. It is desirable to exhaust the air from the air springs to provide a stable trailer deck for safely loading and unloading cargo from the trailer or truck.
A difficulty associated with conventional arrangements is that when the trailer or rear end of the truck drops as air is exhausted from the air springs, there is an undesirable mismatch between the trailer deck height and the loading dock height. Under some circumstances, a mismatch between the trailer deck height and the dock height prevents a forklift or other vehicle from moving into and out of the trailer for unloading the cargo.
One proposed solution has been to include a non-dump height control valve such that air is not evacuated from the air springs when parking brakes are applied. This solution is not ideal, however. In many instances, attempting to load or unload a trailer without first exhausting air from the air springs results in undesirable bouncing and creates a possible safety concern. It is best to have the truck or trailer as stable as possible during loading or unloading operations.
Accordingly, there is a need for a safe and stable arrangement that allows loading and unloading a trailer while maintaining a desired height of the deck or bed of the truck or trailer. This invention addresses that need and avoids the shortcomings and drawbacks of prior attempts.
In general terms, this invention is a vehicle suspension having a dock height holding device. A suspension assembly designed according to this invention includes a first support member attached to a body of the vehicle such as a truck trailer. A second support member moves relative to the first support member. At least one air spring is coupled with the first and second support members. A jounce bumper within the air spring has a first portion supported relative to the first support member and a second portion supported to move with the second support member. The jounce bumper portions each include cooperating surface configurations that maintain a first minimal spacing between the support members when the first and second portions are in a first alignment position. This position is useful during normal driving conditions. The surface configurations on the jounce bumper portions maintain a second spacing between the support members when the first and second jounce bumper portions are in a second alignment position. This position is useful to maintain a dock height during loading or unloading of the truck or trailer, for example.
In one example, each jounce bumper portion surface configuration includes four projections equally spaced about a circumference of the jounce bumper portion. Between each projection is a recess that is sized to receive the projections on the oppositely facing jounce bumper portion. In this example, rotating one of the jounce bumper portions 45 degrees allows moving the jounce bumper portions between the first and second alignment positions.
In another example, the surface configurations of the jounce bumper portions include sloped surfaces that are generally parallel to each other when the jounce bumpers are in the first alignment position. As one of the jounce bumper portions is progressively rotated, the height maintained by the contacting surfaces increases. This particular example provides a wide versatility for adjusting the height holding feature of the inventive device to accommodate the particular needs of a variety of situations.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.